Disease: Contact Dermatitis

    Contact dermatitis facts

    • Contact dermatitis is a rash that occurs at the site of exposure to a substance capable of producing an allegic or irritant skin response.
    • Contact dermatitis can be caused by noxious, irritating substances or substances to which the patient has developed a skin allergy.
    • Patients with contact dermatitis complain of itching and burning at the site of a red, elevated, crusty, weepy, scaly rash.
    • Contact dermatitis is diagnosed by its clinical appearance associated with a compatible history from the patient. Confirmation of allergic contact dermatitis may require a skin challenge with the suspected substance. In addition, other eczematous eruptions must be considered and rejected.
    • Contact dermatitis generally requires treatment with topical steroid creams, but if extensive, may require taking steroids orally.
    • The prognosis is good if the provoking substance can be identified and avoided.
    • Prevention involves avoiding skin contact of irritating and allergenic substances.

    What is contact dermatitis?

    Contact dermatitis is a rash that occurs at the site of exposure to a substance that inflames the skin.

    What causes contact dermatitis?

    There are two forms of contact dermatitis. Irritant contact dermatitis occurs at the site of application of toxic chemical or substance which is directly noxious to skin. The second, allergic contact dermatitis, is an itchy rash that occurs only in people who have developed an allergic sensitivity to that particular chemical or substance. Such substances are not necessarily irritating or toxic although they may be. They are capable of inducing an immune response in the skin at the site where the direct contact occurs. This requires at least one previous contact in the past with that substance to allow the immune system to be primed to react to that substance when it is encountered again.

    What are risk factors for contact dermatitis?

    Contact dermatitis is caused by the direct application of the inciting substance to unprotected skin. Therefore, the key risk factor is exposure to that substance.

    What are contact dermatitis symptoms and signs?

    Contact dermatitis appears as a weepy, oozy, red, elevated rash (an eczematous dermatitis) at the site of direct contact with the inciting substance. The major complaint of most patients is itching or burning at that site. Older lesions are itchy but may only appear as red, elevated, and scaly.

    How is contact dermatitis diagnosed?

    Irritant contact dermatitis is diagnosed by its clinical appearance associated with appropriate historical clues furnished by the patient during the medical interview. The incubation period between exposure and the onset of symptoms is minutes to hours so that the patient usually is aware of the identity of the causal substance. Allergic contact dermatitis is much more difficult to diagnose. The pattern of the distribution of the eczematous dermatitis is frequently helpful. For example, allergic contact dermatitis to poison oak, poison ivy, or poison sumac (Toxicodendron plants) typically appears as a linear eruption because the affected skin moves past the leaves of the plant in a line, distributing the allergenic material linearly. The induction of sensitivity requires at least one previous exposure. However, for mildly allergenic substances, many exposures may be necessary before an allergy is manifest. To correctly identify a particular allergen, it may be necessary to use a challenge technique called "patch testing" to confirm which substance is the cause. This requires at least a 48-hour application of the potential allergen to the skin under an occlusive covering. The development of eczema at the test site within two to five days after removal of the occlusive material confirms the presence of allergy to that substance. Other eczematous eruptions need to be excluded. This may require culturing for microorganisms, an evaluation of skin scrapings and scale, and perhaps a microscopic examination of a small piece of affected skin removed surgically for biopsy.

    What are risk factors for contact dermatitis?

    Contact dermatitis is caused by the direct application of the inciting substance to unprotected skin. Therefore, the key risk factor is exposure to that substance.

    What are contact dermatitis symptoms and signs?

    Contact dermatitis appears as a weepy, oozy, red, elevated rash (an eczematous dermatitis) at the site of direct contact with the inciting substance. The major complaint of most patients is itching or burning at that site. Older lesions are itchy but may only appear as red, elevated, and scaly.

    How is contact dermatitis diagnosed?

    Irritant contact dermatitis is diagnosed by its clinical appearance associated with appropriate historical clues furnished by the patient during the medical interview. The incubation period between exposure and the onset of symptoms is minutes to hours so that the patient usually is aware of the identity of the causal substance. Allergic contact dermatitis is much more difficult to diagnose. The pattern of the distribution of the eczematous dermatitis is frequently helpful. For example, allergic contact dermatitis to poison oak, poison ivy, or poison sumac (Toxicodendron plants) typically appears as a linear eruption because the affected skin moves past the leaves of the plant in a line, distributing the allergenic material linearly. The induction of sensitivity requires at least one previous exposure. However, for mildly allergenic substances, many exposures may be necessary before an allergy is manifest. To correctly identify a particular allergen, it may be necessary to use a challenge technique called "patch testing" to confirm which substance is the cause. This requires at least a 48-hour application of the potential allergen to the skin under an occlusive covering. The development of eczema at the test site within two to five days after removal of the occlusive material confirms the presence of allergy to that substance. Other eczematous eruptions need to be excluded. This may require culturing for microorganisms, an evaluation of skin scrapings and scale, and perhaps a microscopic examination of a small piece of affected skin removed surgically for biopsy.

    Source: http://www.rxlist.com

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